Oriented polypropylene films are useful for wrapping, bagging, and otherwise “enveloping” many types of products from food items to hardware. Due to the heavy volume of oriented polypropylene film used by packagers, there is always a desire to downgauge to save money and weight. But, in order to do this the polypropylene compositions used to make the films must be able to make films at least as strong, for example by having the same modulus, as those of the original film. While this may be accomplished by, for example, using highly crystallizable polypropylene, there is usually a tradeoff in processability. The tougher the film is, typically, the tougher it is to extrude and stretch. What would be desirable is a polypropylene composition that can be used to make strong (high modulus) films while also being easily processable, or at least as processable as its thicker counterpart. The inventor here has accomplished this.
Examples of using hydrocarbon resins in the core layer of polypropylene films can be found in US 2007/0082157. Other related publications that disclose “soft” polymers in the core layer include WO 2010/047905, WO 2010/120295, US 2003/0143357, US 2007/0292682, US 2009/0087648, US 2009/0136698, U.S. Pat. Nos. 7,537,829, and 6,303,233.